What is Azure Virtual Network (VNet)?

Definition: Azure Virtual Network allows azure resources like VM, Database, Apps to communicate with each other.

• You can think of Virtual Network as a set of resources that connect other resources.
• This is called a virtual network because you can access the network, but you don’t have any access to the hardware components.
• A VNet belongs to a single region. So, all the resources in a VNet also must be in the same region. You can connect VNets to communicate between Regions.
• One VNet belongs to one/single subscription but One subscription can have multiple VNets.

There are some concepts you need to understand before we dive into VNet.

1. IP Address:
   1. When you send a courier to someone, you write a postal address on it so that the courier company knows exactly where the package needs to be delivered.
   2. Similarly, every request on the internet has an address (IP address), so that the internet or WWW knows exactly where the response needs to be sent back.
2. Address Space:
   1. An address space is a range of IP addresses that are available.
   2. Every service or resource that is connected to VNet, will get a unique IP address within the range of address space. That is how services will communicate with each other within the same VNet.
   3. You assign address space to VNet and all the services, resources connected to that VNet will automatically get an IP address.
3. Subnets:
   1. You can divide a VNet into multiple Subnets. Subnet lets you segment a VNet into smaller networks that make logical sense.
   2. Each Subnet will get a portion of address space as shown in the screenshot below.
   
4. Because of Subnet, you will have multiple networks on the same VNet.
5. This gives some advantages like,
   1. Resource Grouping: Same services will go together in a single subnet. It will help in keeping track of services.
   2. Address Allocation: Address allocation becomes more efficient. This is the prime advantage of subnets.
   3. Subnet Security: You can use a network security group to secure individual subnets.

Azure Virtual Network capabilities and advantages

• You can create multiple isolated Virtual Networks (VNets) using Azure. Resource grouping and Address Allocation come in handy over here.
• You can add more VNets or more addresses as and when required.
• Using Azure VNets, you can connect not only VMs but other services too like Azure Kubernetes Service, Azure VM Scale Set, App service environment for Power Apps, etc.
• Within your Azure subscription, Azure VNets enables you to connect to your On-premises resources also
• You can route and control the traffic between the Subnets using Route Tables and Border Gateway Protocol.
• You can also filter the traffic between the Subnets using Network Security Groups and Network Virtual Appliances.

What is VNet Peering?

• This feature lets you connect two or more VNets in Azure.
• VNet Peering is the fundamental part of using Virtual Networks (VNets).

• Traffic between the Virtual Machines in Peered network uses Private Microsoft backbone network and it never passes through Public Network.
• Peering provides low-latency and high bandwidth connection between the resources in the different Virtual Networks (VNets).
• With the help of Peering, Resource in different VNets can communicate with each other.
• IMP: Using Peering, the users can transfer data between subscriptions, deployment models, and different regions.